In August, Yammer CEO David Sacksraised a storm when he wrote on Facebook that "Silicon Valley as we know it may be coming to an end."

Since he'd just sold Yammer to Microsoft for $1.2 billion, people paid close attention to his words.

There were too few ideas, Sacks argued, that had escaped the attention of the big Internet players, could be built for less than $5 million, and wouldn't get caught up in patent lawsuits.

But surprisingly, Sacks has kept investing in what most people would call Internet startups. This week, Fresh, a gadget-reviews site, revealed that Sacks was a major backer, as did Houzz, a marketplace for home-remodeling services, last month.

And last October, Sacks backed Twist, an app which alerts colleagues and family members when you're running late.

Here's how Sacks explained his investment in Twist to us: "Twist is at the intersection of the internet and physical world." It actually tracks your location and delivers a realistic estimate of how late you'll be to your next appointment. That, in his mind, made it a "new category" of app—unlike, say, traditional Web-based calendars which just send you reminders of appointments.

Fresh and Houzz have their own, er, twists on purely online models.

Fresh lets would-be reviewers sign up to get review units from manufacturers—and only lets them post reviews after they've received an item.

Houzz lets people assemble "ideabooks" for remodeling or redecorating their homes—and also find professionals who can turn those ideas into reality. The connections may happen online, but the work takes place in the physical world. (As with Twist, it didn't hurt that he was an enthusiastic user.)

So it turns out there are some ideas that fit Sacks's exacting requirements—more, perhaps, than he envisioned last August.

Sacks gave us some thoughts via Twitter:

@owenthomas Houzz is disrupting an industry, home design, that wasn't previously a technology category. That's why it fits my thesis.